Lake_Tana Lake Tana (also spelled T'ana, Amharic:Ṭānā Hāyḳ,"Lake Tana," an older variant is Tsana, Ge'ez ጻና Ṣānā; sometimes called "Dembiya" after the region to the north of the lake) is the source of the Blue Nile and is the largest lake in Ethiopia. Located in the north-western Ethiopian highlands, according to the Statistical Abstract of Ethiopia for 1967/68, the lake is approximately 84 kilometers long and 66 kilometers wide, with a maximum depth of 15 meters, and an elevation of 1,840 meters.